Rudolf Fleischer Thomas Kamphans Rolf Klein Elmar Langetepe Gerhard Trippen Competitive Online Approximation of the Optimal Search Ratio. 881-898 2008 38 SIAM J. Comput. 3 http://dx.doi.org/10.1137/060662204 db/journals/siamcomp/siamcomp38.html#FleischerKKLT08